1. Field of the Invention
The invention relates in general to frequency-selective limiters and, in particular, to frequency-selective limiters using multiple LC-resonant circuits.
2. Description of Prior Art
The ideal frequency-selective limiter operates as a bandpass filter for all input signals within its bandwidth and at power levels below a threshold value and limits the output due to input signals above the threshold value to the threshold value. The need for frequency selective limiting in wide-band receivers is well recognized. This is especially true in military communication systems where strong signals of a hostile or an indifferent nature are present at the same time that there is a need to receive much weaker signals.
In general, the frequency-selective limiting is accomplished by performing a frequency partition in the front end to form separate channels, separately limiting the signals in each channel, and then recombining the channels to a single port. In the case of military communications systems, a receiving system having a very large bandwidth, 2 MHz to 30 MHz for example, may be required. In such a situation a large number (100-1,000) of separate channels are necessary to provide the desired frequency-selective limiting. Typically the frequency partitioning is provided by a series of contiguous bandpass filters, each consisting of a cascade of resonators. In addition to introducing unwanted phase shifts into the system which complicate the task of recombining the outputs, the necessary large number of cascaded resonators limits the number of channels in a practical device because of the space, weight and expense required.